The use of measuring instruments and imaging appliances often necessitates changes in the position or orientation of the measuring instrument depending on the type of measurement to be taken. For example, imagers or for obtaining x-ray images, such as the mobile or swivel-mounted x-ray imagers commonly used in surgery may be used to obtain images with the apparatus at different positions. Image intensifiers and c-arm appliances are examples of such imagers.
With imagers, such as x-ray apparatuses used in surgery, the orientation of the imager relative to the gravitational field of the Earth may have an influence, due to material deformations, on the measurement and, consequently, on the digitization of the image. With x-ray imagers using magneto-optical image digitization, the orientation of the apparatus relative to the Earth's magnetic field may also have a negative effect on the x-ray photographs (images). A further possible deformation of these x-ray images may be due to the influence of optical deformations occurring in the receiver, depending primarily on the composition of the radiation source and on the nature of the receiver, which may arise, for example, during the transformation of electrons into photons or during a subsequent transformation of the photons into an electrical signal.
A system for detecting the position and orientation of a surgical instrument or device within an object and for simultaneously displaying previously generated images corresponding to the detected position and orientation is disclosed in U.S. Pat. No. 5,383,454 to Buchholz. The Buchholz patent discloses that the tip of a probe can be moved to a defined position within the object with the location of the probe being observable on a single display screen, which simultaneously displays a previously generated image of the object. The position of the probe is determined by means of a three-dimensional sound digitizer.